Carbon nanotubes are materials having cylindrical structures of rolled graphene sheets and having one-dimensional structures with significantly large aspect ratios (see Non Patent Literature 1). It is known that carbon nanotubes have excellent mechanical strength, flexibility, semiconductive or metallic conductivity, and high chemical stability. Methods of producing carbon nanotubes such as arc discharge, laser vaporization, and chemical vapor deposition (hereinafter referred to as CVD) have been reported. In particular, CVD is a synthesis method that has received attention as a synthetic method suitable for large-quantity synthesis, continuous synthesis, and high purification (see Non Patent Literature 2).
In particular, it is verified that single-walled carbon nanotubes (hereinafter referred to as “SWCNTs”) exhibit metallic characteristics or semiconductive characteristics depending on the manner of winding and the diameter of the nanotube, and SWCNTs have been expected in applications to electrical and electronic elements and the like. SWCNTs have been synthesized mainly by a catalytic CVD method of growing nanotubes (for example, see Non Patent Literature 3). The catalytic CVD method uses metal nanoparticles as a catalyst. While a gaseous carbon source is being fed, the carbon source is pyrolyzed at a high temperature to grow nanotubes from the metal nanoparticles as the catalyst.